It is certainly what you could call a gem of a discovery. Astronomers believe they have found an entire planet made of diamonds. Scientists at the University of Manchester think they have unearthed a once-massive star in the Milky Way that has been transformed into a small planet made of the precious rock. The international research team first detected an unusual star, called a pulsar, and followed up their discovery with research using a telescope based in an observatory in Cheshire. The findings led the scientists to discover the gravitational pull of a small companion planet orbiting the pulsar. Pulsars are small spinning stars more than ten miles in diameter – the size of a small city – that emit a beam of radio waves. The team thinks that the ‘diamond planet’ is all that remains of the original star, most of whose matter was siphoned off towards the pulsar. The companion planet is small, at less than 40,000 miles wide – about five times the diameter of Earth. But it is so close to the pulsar that if it were any bigger it would be ripped apart by the gravitational force of the star, which rotates more than 10,000 times per minute and has a mass of about 1.4 times that of the sun.